Composition for and method of cleaning and coating metal



Patented Sept. 24,1946

UNITED STAT-E -COMPOSITION FOR AND METHOD OF CLEANING AND COATING METAL Sydney G. Thornbury, Los Angeles, Calif,,

or to Turco Products, Inc., Los Angeles, a corporation of California Application September 17, 1943, Serial No. 502,817

3 Claims. (Cl. 148-6) No Drawing.

This invention relates to the cleaning and preparation of metal surfaces preparatory to painting and the like.

It is well known that adhesion of paint to metals is materially improved if the metals are treated and prepared with dilute solutions of phosphoric acid prior'to application of the paint. The acid roughens or 'etches the surface and deposits metallic phosphate. But before the phosphoric acid can act upon the metal it is essential that the metal be cleaned of interfering films of grease, oil, metallic oxides, etc.

Heretofore in some commercial phosphating operations, the metals have been first cleaned by degreasing in a hot water bath containing alkaline cleaning agents, or by vapor degreasing with trichlorethylene or' similar solvents. Where rust is present onthe metal it has been removed by pickling with sulphuric acid, by sand blasting, or the application of steel wool or sandpaper.

1 Such operations require special equipmentand considerable time. 7

' It is highly desirable to be able to combine the cleaning and, phosphating actions so as to complete the treatment in a single, simple operation. Many attempts have been made in this direction but those attempts have lacked efliciency and dependability and have left much to be desired.' For instance, previous workers in the art have combined water solutions of phosphoric acid with water-soluble solvents such as isopropyl alcohol, the ketones, glycol ethers, and the like, and, in some instances, have included in the solution acid-stable wetting agents having soap-like properties, such, for instance, as alleyl aryl sulfonates, secondary alcohol sulfonates, saponin and others.

. thereon a thin but strongly adherent coating of assls'n- Calif bines a direct solvent action for the grease with an acid solution. The best solvents for oils and greases are the hydrocarbons to which they are chemically related and in which they are infinitely soluble, and I have found it possible to combine such solvents with a water solution of phosphoric acid by providing a coupling agent or agents to combine the aqueous phase with the hydrocarbon phase, thus presenting a uniform, clear solution. It is,'therefore,-one of the principal purposes of my invention to provide a metal cleaning and treating solution wherein the etching. and cleaning agents are combined into a solution which may be used to complete the cleaning and treating in a single operation.

In carrying out my invention I utilize as the solvent a hydrocarbon, such as kerosene, the aromatic solvents of petroleum or coal tar origin, or "Stoddard solvent. I add sufilcient water to dilute the acid tothe desired concentration and to render it chemically active,- and add a combination of butanol and ethanol as a coupling agent. I find that neither the butanol alone nor the ethanol alone will provide the necessary coupling effect, so that the combination of the two chemicals is required for my preparation and method. For a solution containing, by weight, 7% of a 75% phosphoric acid and 13% water, which is sufiicient water content to provide the necessary dilution and activation of the phosphoric acid, I find that the proportions of butanol and ethanol arerather critical-that is,

However, water solutions of such solvents are of limited efiiciency as degreasing agents, inasmuch as they are true solvents for oils and greases only in the absence of water. Thus, such compounds must depend for their effectiveness entirely upon their emulsifying and wetting power plus the manual scouring action attending their applicaovercome by providing-a compound which com- Example 1 Per cent 75% phosphoric acid 7.00

Water 13.00 Aromatic petroleum solvent 26.00 Ethyl alcohol 21.40 Butanol 32.60

the butanol content must be not less than approximately 25% and not more than approximately 33% by weight, and the ethanol must be not less than approximately 21% and not more than 29% by weight. Thus, my preferred formula is substantially as follows:

I find, however, that reasonable efllciency is obtained from formulas in which the butanol and ethanol proportions are varied within the above-mentioned ranges, fOr instance as shown by the following examples:

The aromatic petroleum solvent utilized in the examples given is one that boils between 365 and 415 F., has an A. P. I. gravity of 31", an aniline point of 5 C., and a kauri-butanol value of 65. The proportions stated in Examples 1, 2 and 3 may be safely varied within a range of 5%.

The solution is wiped onto the metal surface, as by rags saturated with the solution, or may be applied by means of a' bristle brush or spray gun. The solvent is then allowed to evaporate from the applied solution, leaving the metal surface cleaned, roughened and coated to receive the paint. In using the term paint I mean to include such products as varnishes, lacquers, enamels, primers, and the like. I find my solution effective on steel and aluminum, and it is effective for cadmium plating, zinc plating. galvanizing or lead. A present highly advantageous use of my solution is in the preparation of vehi- 4 cle bodies for repainting without the usual paint removing operation preparatory to applying the new paint. While my solution is not intended as a paint remover, it softens and roughens the existing paint, destroying the slick, smooth surface to which additional paint coats will not normally adhere. It removes any loose, oxidized pigment which would prevent paint adhesion. Where the paint has been rubbed on or has peeled, it derfists and phosphatizes the exposed metal surface.

I claim:

1. A composition for removing oil, grease, metal oxide and the like from and depositing a metallic phosphate coating on metal which comprises a solution consisting of water, phosphoric acid, 'aromatic petroleum solvent, and a coupling agent comprising, by weight, 25-33% of butanoi and 21-29% of ethanol; v

2. The method of cleaning a metal surface of grease, oil, metallic oxides and the like and deplied solution.

3. A compositionfor removing oil, grease, metal oxide and the like from and depositing a metallic phosphate coating on metal, which comprises a solution consisting of the following, by weight: 7% of phosphoric acid, 13% water, 26%

. aromatic petroleum solvent, 21.4% ethyl alcohol and 32.6% butanol, and wherein the aromatic petroleum solvent content is one having substantially the following" characteristics: an aniline point of 5 C. and a kauri-butanol value of 65.

SYDNEY G. THORNBURY. 

